Lock-Up System

Lock-up System
In D4 position (3rd and 4th), and D4 position (3rd), pressurized fluid is drained from the back of the torque converter through a fluid passage, causing the lock-up piston to be held against the torque converter cover, As this takes place, the mainshaft rotates at the same speed as the engine crankshaft. Together with hydraulic control, the PCM optimizes the timing of the lock-up mechanism. When the lock-up control solenoid valve activates, modulator pressure changes to switch lock-up ON and OFF. The lock-up control valve and the lock-up timing valve control the range of lock-up according to A/T clutch pressure control solenoid valves A and B. The lock-up control solenoid valve is mounted on the torque converter housing, and A/T clutch pressure control solenoid valves A and B are mounted on the transmission housing. They are controlled by the PCM.

General Operation





1. Operation (clutch on)
With the lock-up clutch on, fluid in the chamber between the torque converter cover and the lock-up piston is drained off, and the converter fluid exerts pressure through the piston against the torque converter cover. As a result, the converter turbine is locked to the converter cover. The effect is to bypass the converter, placing the vehicle in direct drive.





2. Operation (clutch off)
With the lock-up clutch off, fluid flows in the reverse of CLUTCH ON. As a result, the lock-up piston moves away from the converter cover, and torque converter lock-up is released.

No Lock-up





The lock-up control solenoid valve is turned OFF by the PCM. The lock-up shift valve receives LC pressure (LA) on the left side, and modulator pressure (6) on the right side. The lock-up shift valve is in the right side to uncover the port leading torque converter pressure (92) to the left side of the torque converter. Torque converter pressure (92) becomes torque converter pressure (94), and enters into the left side of the torque converter to disengage the lock-up clutch. The lock-up clutch is OFF.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

Partial Lock-up





As the speed of the vehicle reaches the prescribed value, the lock-up control solenoid valve is turned ON by the PCM to release LC pressure (LA) in the left side of the lock-up shift valve. The lock-up shift valve is moved to the left side to switch the port leading torque converter pressure to the left side and right side of the torque converter. Torque converter pressure (92) flows to the right side of the torque converter to engage the lock-up clutch. The PCM also controls A/T clutch pressure control solenoid valves A and B. and LS A or LS B pressure is applied to the lock-up control valve and the lock-up timing valve. The position of the lock-up control valve depends on torque converter pressure and LS A or LS B pressure. When LS A or LS B pressure (58) is lower, torque converter pressure (92) from the regulator valve passes through the lock-up control valve, and flows to the left side of the torque converter to disengage the lock-up clutch. LS A and LS B pressure increase, and higher pressure is applied to the lock-up control valve to release torque converter back pressure. Torque converter back pressure goes lower, and this allows a greater amount of pressure to work on the lock-up clutch to engage the lock-up clutch. Under this condition, the lock-up clutch is controlled by pressure from the right side (to engage the lock-up clutch) and the left side (to disengage the lock-up clutch); the lock-up clutch is in partial lock-up condition.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

Full Lock-up





When the vehicle speed further increases, the PCM controls AM clutch pressure control solenoid valves A and B to increase LS A or LS B pressure (58). The LS A or LS B pressure;(58) is applied to the lock-up control valve and the lock-up timing valve, and moves them to the left side. Under this condition, torque converter back pressure (F2) is released fully, causing the lock-up clutch to be fully engaged.

NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.

Shift Lever/Sequential Sportshift Mode Mechanism
The shift lever has 8 position: P, R, N, D4, D3, 2, 1 positions, and the sequential sportshift mode position. The shift lever shifts between positions along the gate in the A/T gear position indicator panel. The shift lever can shift out of P position and into R position without depressing the shift lever. The shift lock/reverse lock mechanism is an additional shift lever lockout mechanism.
The shift lever is engaged with the shift cable bracket in P, R, N, D4, D3, 2, positions. This unit shifts the transmission using the shift cable connected between the shift cable bracket and the transmission control shaft.





In the sequential sportshift mode position, the shift lever is disengaged from the cable bracket, and the shift lever can be used to shift nears electronically between 1st through 4th, much like a manual transmission.





When the shift lever shifts to the sequential sportshift mode position, the shift lever releases the lock lever, and the lock lever pops up to engage the shift cable bracket to the detent bracket; the shift cable bracket and the shifting positions in the transmission are held in D4 position. The lock lever receives its spring load, pops up in the sequential sportshift mode position, and is depressed by the shift lever and does not engage the shift cable bracket to the shift lever base bracket in any position except sequential sportshift mode.





The shift lever fits into the sequential sportshift mode position by using a detent plunger with a spring. When shifting to upshift or downshift positions, the detent plunger is depressed by the detent bracket inner wall, and the detent plunger spring puts the shift lever back into the neutral position. The detent plunger also works in P position.

Shift Lock/Reverse Lock Mechanism
The shift lock system reduces the risk of unintentional engine starting. Starting the engine is possible only in P and N positions. The shift lock system and the key interlock system make up the interlock control system. The key interlock mechanism is located in the steering lock assembly.
The shift lock mechanism consists of the shift lock solenoid, shift lock stop, shift lock release, and related parts. The reverse lock mechanism shares the shift lock solenoid with the shift lock mechanism, and the reverse lock stop and the shift lock stop are interlocked with the shift lock solenoid operation. The shift lock solenoid is electronically controlled by these shift lock control system signals: brake signal, interlock control signal, and A/T gear position switch position signal. If the shift lock solenoid does not operate, the shift lock/reverse lock mechanism can be released by depressing the shift lock release.





In P position while depressing the brake pedal, the shift lock solenoid is turned ON, and the shift lock solenoid plunger is retracted to release the shift lock stop. This allows the shift lever to be moved.





When the brake pedal is released, the shift lock solenoid remains OFF, and the shift lock stop locks to block the shift lever in N position.





When the shift lever is shifted to R position from D4 position and N position (under certain conditions), the shift lock solenoid is turned ON, and the shift lock solenoid plunger is retracted to release the reverse lock stop. This allows the shift lever to be moved to R position.





If the allowable conditions of turning ON the solenoid are not met, the shift lock solenoid remains OFF, and the reverse lock stop locks to block the shift lever in the N position.